System for managing gas contained in a floating structure

Abstract

The invention relates to a system (1) for managing a gas contained in a tank (2), comprising at least one supply circuit (6), at least one heat treatment circuit (8), at least one first heat exchanger (13), at least one cooling circuit (17), at least one second heat exchanger (16), characterized in that the heat treatment circuit (8) is connected to the at least one second heat exchanger (16). The heat treatment circuit (8) comprises at least one first branch (9) connected to a first compression stage (11) of the compression means (7) and a second branch (10) connected to a second compression stage (12) of the compression means (7), said first branch (9) and said second branch (10) meeting at a convergence point (14) in said heat treatment circuit (8).

Description

Technical Field

[0001] The present invention relates to the field of floating structures for the storage and / or transport of liquid gases and more particularly to systems for managing the storage and / or transport of gases within such vessels. Background Art

[0002] During a trip performed by a floating structure comprising tanks for liquid gas intended to be consumed and / or transported to a destination point, said floating structure may tend to use the gas boiled off inside the tanks and then compress said gas in order to supply the engine(s) of the floating structure.

[0003] It is further known to reliquefy the gas, in case of excess boil-off gas in the tank, by passing the gas not yet used to supply the engine(s) of the floating structure through one or more heat exchangers and then returning the gas to the tank.

[0004] However, it happens that certain floating structures and more particularly the tanks they comprise are allowed to store and / or transport different types of liquid gases. Thus, the floating structure may for example comprise a liquefied natural gas cargo consisting almost exclusively of methane, or indeed an ethane cargo which may contain a small proportion of methane.

[0005] The different types of gases present different chemical structures relative to each other. Through the said differences in structure, other properties distinguish one gas from another, such as evaporation temperature or compatibility with at least one of the devices integrated into the floating structure and adapted to consume the gas, such as an engine.

[0006] Therefore, using the gas in the tank as fuel or reliquefying it according to its properties (depending on its different parameters) may be complicated, certain situations may not be optimally compatible with the system used, and this may compromise the efficiency of the gas reliquefaction. Summary of the invention

[0007] The invention allows adapting to different types of gases stored and / or transported and in this way proposes a management system for managing gas contained in at least one tank of a floating structure comprising at least one gas consuming device, the management system comprising:

[0008] at least one gas supply circuit of the gas-consuming device, the supply circuit comprising at least one compression device comprising at least two compression stages and configured to compress the gaseous gas extracted from the tank to a pressure compatible with the needs of the gas-consuming device,

[0009] at least one gas processing circuit for gaseous gas compressed by at least one compression stage of a compression device,

[0010] at least a first heat exchanger configured to carry out heat exchange between the gaseous gas circulating in the supply circuit between the tank and the compression device and the gaseous gas circulating in the thermal treatment circuit,

[0011] at least one cooling circuit including at least one pump configured to extract liquid gas from the tank,

[0012] at least a second heat exchanger configured to carry out a heat exchange between the gaseous gas circulating in the heat treatment circuit and the gas circulating in the cooling circuit downstream of the first heat exchanger,

[0013] Characterized in that the heat treatment circuit comprises at least a first branch connected to a first compression stage of the compression device and a second branch connected to a second compression stage of the compression device, the second compression stage being arranged downstream of the first compression stage, and the first branch and the second branch being joined together at a convergence point of the heat treatment circuit.

[0014] Thanks to this management system, the gaseous gas contained in the tank can be consumed and also optimally liquefied, regardless of its nature. Depending on the characteristics of the gas stored and / or transported, and also on the compatibility of said gas with the gas consuming device, the management system can be adapted to obtain a system-efficient gas treatment. The compression stage as described in the present invention can correspond to a plurality of compressors.

[0015] The supply circuit is used to suck in the gaseous gas formed at the head space of the tank. The gaseous gas is due to the evaporation of part of the contents of the liquid gas contained in the tank. This evaporation can occur naturally or forced by some means integrated into the floating structure. The gaseous gas can thus be consumed or reliquefied, but usually has to be discharged to regulate the pressure in the tank.

[0016] Therefore, the compression device provides the suction of the gaseous gas and compresses the gas. The compression device can be, for example, a plurality of compressors arranged in series relative to each other, or a single compressor with a plurality of compression stages. The greater the number of compression stages through which the gaseous gas passes, the higher the pressure to which the gaseous gas is subjected. The gas compressed by the entire compression device can reach a pressure comprised between 250 bar and 400 bar. The pressure applied to the gaseous gas is important for supplying the gas consumption device, because the gas consumption device can consume the gaseous gas only when the gas is at a compatible pressure. In addition, depending on the chemical structure of the gas, the gas consumption device may not tend to consume the gas contained in the tank.

[0017] In this configuration, the gaseous gas is then not discharged from the tank for supply purposes.

[0018] If the gaseous gas is incompatible with the gas consumer or if it is not necessary to supply the gas consumer, the gaseous gas circulates in the heat treatment circuit. If the gas consumer only needs to be supplied with a portion of the gaseous gas, the remaining gaseous gas also circulates in the heat treatment circuit. One of the functions of the heat treatment circuit is to participate in the reliquefaction of the compressed gaseous gas.

[0019] The first heat exchanger serves to precool the compressed gaseous gas and to heat the gaseous gas at the output of the tank. Precooling of the compressed gas makes its subsequent thermal treatment easier, in particular for example its reliquefaction. Thus, the first heat exchanger serves to improve the overall efficiency of the management system, since the low temperature of the gaseous gas at the output of the tank indirectly participates in the reliquefaction of the compressed gaseous gas via the heat exchange taking place in the first heat exchanger.

[0020] The cooling circuit can have various functions, for example, it participates in the reliquefaction of the gaseous gas circulating in the heat treatment circuit, or in the management of the tank pressure. To this end, the liquid gas in the tank is sucked by a pump, which is for example immersed in the bottom of the tank and circulates the liquid gas in the cooling circuit.

[0021] By circulating through the cooling circuit, the liquid gas can flow through a second heat exchanger which also allows the passage of the gaseous gas circulating in the heat treatment circuit. The heat exchanger thus makes it possible to reliquefy the gaseous gas without causing evaporation of the liquid gas circulating through the cooling circuit. Once the gaseous gas is reliquefied, the latter can be returned to the tank, just like the liquid gas used for reliquefaction by circulating in the cooling circuit.

[0022] An advantage of the heat treatment system according to the invention is that there are multiple branches at the output of the compression device within the heat treatment circuit. Thus, regardless of the nature of the gas contained in the tank, the gas can be systematically consumed and / or optimally reliquefied. As an example, a gas intended to be consumed at a low pressure (whose reliquefaction is more efficient at low pressure) can come out of the compression device at a first compression stage, while a gas intended to be consumed at a high pressure (whose reliquefaction is more efficient at high pressure) can come out of the compression device at a second compression stage. The same is true for a gas intended to be consumed at a high pressure and whose reliquefaction is more efficient at a low pressure, and vice versa.

[0023] Connecting to the first compression stage and the second compression stage means that the first branch is connected to the output of the first compression stage, and the second branch is connected to the output of the second compression stage. In other words, the first compression stage is the last stage that compresses the gaseous gas circulating in the first branch, and the second compression stage is the last stage that compresses the gaseous gas in the second branch.

[0024] The gas compressed by the compression device up to the first compression stage has a pressure comprised between 7 and 20 bars. The gas compressed by the compression device up to the second compression stage has a pressure comprised between 120 and 150 bars. In such a configuration, the gas can come out of the compression device at two different compression stages. The two branches are then merged so that the compressed gas is treated in the heat treatment circuit, regardless of the pressure at which the gas is compressed.

[0025] As mentioned above, the management system may be adapted to the nature and / or composition of the gas contained in the tank. Thus, in the case where the floating structure and its tanks are configured to transport and / or store gas (such as methane or ethane), the management system is configured to allow the gas to circulate in the first branch and / or in the second branch if the gas contained in the tank is methane, and to circulate only in the first branch if the gas contained in the tank is ethane. This configuration serves to handle each type of gas as well as possible in terms of supply and / or reliquefaction.

[0026] According to a feature of the invention, the convergence point is arranged between the compression device and the first heat exchanger. It is particularly advantageous to precool the compressed gas, whatever the pressure to which the gas is compressed. The convergence point is thus preferably positioned upstream of the first heat exchanger with respect to the flow direction of the compressed gas.

[0027] According to a feature of the invention, the heat treatment circuit comprises at least one expansion member arranged downstream of the first heat exchanger. After having been precooled, the gaseous gas is expanded in order to reduce its pressure, thereby cooling the gas even more, or even reliquefying the gas. Expansion can also be carried out, for example, in the case where the gas is ethane and the goal is to produce a two-phase mixture, in order to extract the methane portion contained in the ethane by keeping the ethane in the gaseous state while the methane is reliquefied. Expansion can contribute to the formation of such a two-phase mixture by changing the phase transition point of the gas by reducing its pressure.

[0028] According to a feature of the invention, the expansion member is arranged between the first heat exchanger and the second heat exchanger. This particular arrangement serves to prepare the gaseous gas for reliquefaction, in particular by means of the second heat exchanger.

[0029] According to a feature of the invention, the second branch of the heat treatment circuit comprises a control member. The second branch is connected to the second compression stage, i.e., to the compression stage in which the gas is compressed to the greatest extent. The control member arranged on the second branch is thus used to control the flow of the gaseous gas of the second branch. If appropriate, in addition to providing flow regulation, the control member can also expand the gaseous gas circulating in the second branch. It can be advantageous to expand the gas before the gas is cooled in the first heat exchanger so that the gas pressure is compatible with the technology of the first heat exchanger.

[0030] According to a feature of the invention, the first branch has no control member.When the gas is compressed only up to the first compression stage, there is no need to expand the gas.

[0031] According to a feature of the invention, the gas consuming device is a high-pressure gas consuming device, and the supply circuit is configured to supply the high-pressure gas consuming device and / or the low-pressure gas consuming device. In other words, there are at least two gas consuming devices, which can be supplied by the gaseous gas contained in the tank. As an example, the high-pressure gas consuming device can be an engine for propelling the floating structure, and the low-pressure gas consuming device can be a generator of the floating structure. These two examples of gas consuming devices can be compatible or incompatible with the gas stored and / or transported in the tank, and have a specific pressure range in the case of compatibility.

[0032] According to a feature of the invention, the supply to the low-pressure gas consumer by the supply circuit is at least partially through the first branch. As mentioned above, the first branch is connected to the first compression stage of the compression device, connected to the stage where the gas is compressed at a low pressure. Therefore, the first compression stage is suitable for compressing the gaseous gas at a pressure compatible with the needs of the low-pressure gas consumer, provided that the low-pressure gas consumer can consume the type of gas contained in the tank. For this reason, the supply of the low-pressure gas consumer is therefore partially consistent with the first branch.

[0033] According to a feature of the invention, the thermal treatment circuit comprises a separation device, the input of which is arranged downstream of the second heat exchanger. The separation device is used to separate the gas phase from the liquid phase of the gas circulating in the thermal treatment circuit after the gas has passed through the second heat exchanger. The separation device can be used in the case of partial reliquefaction of the gas circulating in the thermal treatment circuit, in order to retain the gas portion that has not been reliquefied.

[0034] According to one feature of the present invention, the separation device includes a first output, which is configured to allow gaseous gas to come out of the separation device, and the heat treatment circuit includes a third branch that connects the first output of the separation device to the supply circuit of the low-pressure gas consumption device. As described above, if the gas contained in the tank is ethane, the heat treatment of the gas can be performed to re-liquefy the ethane while keeping the methane in a gaseous state so that the methane exists in the ethane with the minimum ratio. Methane can then circulate outside the separation device via the first output, and then circulate inside the third branch to supply the low-pressure gas consumption device. The latter does not tend to consume ethane, and the only means of supplying gaseous gas therein is to separate the methane contained in the ethane and provide the methane.

[0035] According to a characteristic of the invention, the heat treatment circuit comprises a fourth branch which connects the first output of the separation device with the supply circuit at a point located between the tank and the first heat exchanger. The fourth branch is used, for example, in the case of partial reliquefaction of the separated gas components without intention. The gaseous gas, which remains gaseous after passing through the second heat exchanger, is then isolated in the separation device and then circulates through the fourth branch in order to recirculate in the supply circuit in order to be consumed or to cause a new attempt at reliquefaction.

[0036] According to a feature of the invention, the separation device comprises a second output configured to allow the liquid gas to exit the separation device, and the heat treatment circuit comprises a fifth branch connecting the second output of the separation device with the cooling circuit. Thus, the reliquefied gas exits the separation device in the liquid state and circulates through the fifth branch in order to return to the tank by joining the cooling circuit.

[0037] According to a characteristic of the invention, the heat treatment circuit comprises a sixth branch connecting the output of the passage of the second heat exchanger constituting the heat treatment circuit with the fifth branch. In other words, the sixth branch bypasses the separation device and joins the cooling circuit directly via the fifth branch. When it is determined that complete reliquefaction of the gas occurs after it has passed through the second heat exchanger, it is advantageous to bypass the separation device in order to prevent unnecessary heat input.

[0038] According to a characteristic of the invention, the management system comprises a third heat exchanger configured to carry out a heat exchange between the liquid gas circulating in the cooling circuit and the refrigerant fluid circulating in the cooling circuit. The third heat exchanger is used to subcool the liquid gas, for example, with the aim of improving the reliquefaction of the gaseous gas circulating through the second heat exchanger by circulating the subcooled liquid gas in the same second heat exchanger.

[0039] The subcooled liquid gas may also be returned to the tank in order to reduce the bulk temperature of the latter and thereby the pressure of the tank.The fluid refrigerant circulating through the cooling circuit for subcooling the liquid gas may be nitrogen, for example.

[0040] According to a characteristic of the invention, the management system comprises an additional branch connecting the first compression stage of the compression device to the tank, the management system further comprising a heat exchanger configured to implement a heat exchange between the gaseous gas circulating in the additional branch and the refrigerant fluid circulating through the reliquefaction loop. It is an alternative embodiment that can be implemented, for example, without the presence of the above-mentioned third heat exchanger, or for treating a large amount of gaseous gas.

[0041] The presence of an additional branch and a heat exchanger can be useful, for example, in the case where the gaseous gas circulating from the tank to the compression device is too low to allow effective precooling. A heat exchanger can also be used when the temperature of the liquid gas contained in the tank is too high to properly reliquefy the gaseous gas circulating in the thermal treatment circuit and the liquid gas cannot be subcooled.

[0042] In this configuration, at least part of the compressed gaseous gas intended to be reliquefied can be circulated in an additional branch and reliquefied by means of the heat exchanger operating within the heat exchanger.As the above-mentioned cooling loop, a refrigerant fluid (eg nitrogen) can flow through the reliquefaction loop.

[0043] An additional branch extends to the tank so that the gas, once reliquefied in the heat exchanger, can flow to the tank in liquid state.

[0044] According to a feature of the invention, the cooling circuit comprises at least one end piece opening in the tank, the end piece being a spray head member and / or an orifice arranged in the lower part of the tank.

[0045] In addition to participating in the reliquefaction of the gaseous gas, the cooling circuit may also participate in the management of the pressure of the tank and the overall temperature of the gas contained on the tank.

[0046] The management system may include a single end piece, which may be the orifice of the sparger member, or may include two end pieces, which include the orifice and the sparger member.

[0047] In order to participate in the cooling of the tank, the liquid gas can circulate in the cooling circuit, be supercooled by means of the third heat exchanger, and then return to the tank via the orifice and / or the sparger member. The orifice provides a return inside the tank so as to reduce the overall temperature of the liquid gas in the tank. The sparger member is used to spray the liquid gas at the head space of the tank, which enhances the condensation of the liquid gas present in the head space of the tank so as to reduce the pressure of the tank.

[0048] The invention also covers a floating structure comprising at least a management system as described above, the tank containing liquefied natural gas.

[0049] According to a feature of the invention, the floating structure comprises at least a management system as described above, the tank containing ethane.

[0050] As mentioned above, the nature of the gas contained in the tank will determine the operation of the management system, how the gas consuming devices are supplied and how the gaseous gas is reliquefied.

[0051] The invention also covers a method of managing gas contained in at least one tank of a floating structure, the method being implemented by a management system as described above, during which method:

[0052] If the gas contained in the tank is liquefied natural gas, the gas circulates through the first branch and / or the second branch of the thermal treatment circuit, or,

[0053] If the gas contained in the tank is ethane, the gas circulates in the first branch of the thermal treatment circuit, preventing the gas from circulating in the second branch.

[0054] The management method is thus used to adapt the management system with regard to gas consumption or reliquefaction, regardless of whether the gas contained in the tank is liquefied natural gas or ethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Other characteristics and advantages of the invention will again emerge from the following description on the one hand and from a number of exemplary embodiments given as indications but without limiting them on the other hand, with reference to the accompanying schematic drawings, in which:

[0056] [ Figure 1 ] is a diagram of a management system for gas contained in tanks within a floating structure,

[0057] [ Figure 2 ] is an example diagram of gas flow when the gas contained in the tank is liquefied natural gas,

[0058] [ Figure 3 ] is an example diagram of gas flow when the gas contained in the tank is ethane.

[0059] [ Figure 4 ] represents an alternative embodiment of the management system according to the present invention. DETAILED DESCRIPTION

[0060] Figure 1 A management system 1 according to the invention is shown. The management system 1 may be integrated in a floating structure, such as a ship for storing and / or transporting liquid gas contained in at least one tank 2. The liquid gas may evaporate naturally and partially in the head space 3 of the tank 2.

[0061] In order to manage the pressure of the tank 2, which is increased due to the presence of gaseous gas in the head space 3, the management system 1 can process the gas so that it supplies at least one gas consumer. Figure 1 In the embodiment, the management system is configured to supply a high-pressure gas consumer 4 and a low-pressure gas consumer 5. The high-pressure gas consumer 4 may be, for example, an engine for propelling a floating structure. The low-pressure gas consumer 5 may be a generator for supplying power to the floating structure. The high-pressure gas consumer 4 and the low-pressure gas consumer 5 each have their own supply gas conditions, which need to have specific properties and specific pressures to be compatible with the needs of each gas consumer 4, 5.

[0062] In order to provide supply to the gas consumers 4, 5, the management system 1 comprises a supply circuit 6 extending from the tank 2 and the high-pressure gas consumer 4. The supply circuit 6 comprises a compression device 7 for sucking the gaseous gas contained in the head space 3 of the tank 2 and compressing the latter to a pressure compatible with the needs of the high-pressure gas consumer 4.

[0063] exist Figure 1 In the figure, the compression device 7 is schematically shown as a series of compressors, but the compression device 7 can also be a single multi-stage compressor. Thus, the compression device 7 has a plurality of compression stages in order to compress the gaseous gas at a variable high pressure. The more compression stages the gaseous gas passes through, the higher the pressure to which the latter is compressed. The gaseous gas can then pass through all the compression stages of the compression device 7 to reach a pressure compatible with the supply of the high-pressure gas consumer 4. The gaseous gas can reach a pressure value included between 250 bar and 400 bar at the output of the entire compression device 7.

[0064] The management system 1 also comprises a heat treatment circuit 8. The heat treatment circuit 8 is connected to the supply circuit 6, more specifically at the compression device 7. The particularity of the management system 1 according to the invention is that the heat treatment circuit 8 comprises a first branch 9 and a second branch 10, which are respectively connected to a first compression stage 11 and a second compression stage 12 arranged downstream of the first compression stage 11. The first branch 9 and the second branch 10 are thus used to circulate the gaseous gas at two different pressure levels within the heat treatment circuit 8. In addition, a part of the supply circuit 6 is connected to the first branch 9 in order to connect the latter to the low-pressure gas consumer 5. This connection is used because the gaseous gas compressed at the first compression stage 11 has a pressure compatible with supplying the low-pressure gas consumer 5. The gaseous gas compressed until the first compression stage 11 has a pressure comprised between 7 and 20 bars, while the gaseous gas compressed until the second compression stage 12 has a pressure comprised between 120 and 150 bars.

[0065] In addition to being connected to different compression stages, the first branch 9 and the second branch 10 differ from each other by the fact that the second branch 10 comprises a control member 32, while the first branch does not have one. The control member 32 serves to regulate the flow through the second branch 10, but can also provide expansion of the gas circulating through the second branch 10 after the gas has been compressed up to the second compression stage 12.

[0066] One of the purposes of the thermal treatment circuit 8 is to participate in the reliquefaction of the gaseous gas not intended for the supply of the gas-consuming means 4, 5, so as to limit the losses associated with the evaporation of the gas contained in the tank 2. To this end, the management system 1 comprises a first heat exchanger 13 configured to implement a heat exchange between the compressed gaseous gas circulating in the thermal treatment circuit 8 and the gaseous gas circulating in the supply circuit 6 upstream of the compression means 7.

[0067] Thus, the first heat exchanger 13 is used to precool the gaseous gas circulating in the heat treatment circuit 8 by using the gaseous gas at the output of the tank 2. The gaseous gas circulating in the heat treatment circuit 8 is then heated by capturing the calories of the latter.

[0068] It should be noted that the first branch 9 and the second branch 10 meet at a convergence point 14. The convergence point 14 is advantageously arranged upstream of the first heat exchanger 13, so that all the gaseous gases circulating in the heat treatment circuit 8 flow through the first heat exchanger 13 to be precooled. However, the management system 1 can be configured in a manner not shown so that the first branch 9 or the second branch 10 bypasses the first heat exchanger 13. In this case, the convergence point 14 is arranged downstream of the first heat exchanger 13.

[0069] The precooled gaseous gas is expanded at the output of the first heat exchanger 13 by means of an expansion member 15. The expansion of the gaseous gas makes it possible to further reduce its pressure and temperature. The expansion member 15 also changes the state change temperature of the gaseous gas. The gaseous gas then flows through a second heat exchanger 16 in order to be at least partially reliquefied. Figure 1 In the embodiment, the expansion member 15 is arranged between the first heat exchanger 13 and the second heat exchanger 16 , but the expansion member 15 may also be arranged downstream of the second heat exchanger 16 .

[0070] In order to operate an effective reliquefaction, the management system 1 comprises a cooling circuit 17 in which the liquid gas extracted from the tank 2 circulates. The cooling circuit 17 comprises a pump 18, which is advantageously immersed in the bottom of the tank 2 and which circulates the liquid gas in the cooling circuit 17. Among the different functions of the cooling circuit 17, one of them is to participate in the reliquefaction of the gaseous gas in the thermal treatment circuit 8. The liquid gas circulating in the cooling circuit 17 can flow through the second heat exchanger 16, in which a heat exchange with the gaseous gas circulating in the thermal treatment circuit 8 takes place. The gaseous gas is then reliquefied.

[0071] In order to improve the reliquefaction of the gaseous gas circulating in the second heat exchanger 16 , the management system 1 comprises a third heat exchanger 19 through which the liquid gas circulating in the cooling circuit 17 can flow.

[0072] The third heat exchanger 19 is used to subcool the liquid gas in order to compensate for the calories captured by the liquid gas during the heat exchange taking place in the second heat exchanger 16. To subcool the liquid gas, the third heat exchanger 19 is also traversed by a cooling circuit 20 through which circulates a refrigerant fluid which subcools the liquid gas. The refrigerant fluid circulating through the cooling circuit 20 may be, for example, nitrogen.

[0073] Once the gas circulating in the heat treatment circuit 8 is at least partially reliquefied, the gas can circulate until a separation device 21 comprising an input 22, in which the gas at the output of the second heat exchanger 16 flows. If the gas is not completely reliquefied, the separation device 21 is used to separate the liquid part of the gas from the vapor part. The separation device 21 comprises a first output 23 allowing the vapor part to exit the separation device 21 and a second output 24 allowing the liquid part to exit the separation device 21.

[0074] The vapor fraction, if present in the separation device 21, can come out via the first output 23 and circulate in the third branch 25 and in the fourth branch 26. The third branch 25 is connected to the low-pressure gas consumer 5 so that the vapor fraction can supply the low-pressure gas consumer 5 if the gas in question can be consumed by the low-pressure gas consumer 5. The fourth branch is connected to the supply circuit 6 and allows the recirculation of the gaseous gas that has not been reliquefied in said supply circuit 6 so that said gas is consumed or reliquefied.

[0075] The liquid portion present in the separation device 21 can exit via the second outlet 24 and circulate in a fifth branch 27, which connects the separation device 21 to the cooling circuit 17. After reaching the tank 2, the gas is reliquefied and then circulated to the tank 2. Figure 1 The fifth branch 27 is connected to the cooling circuit 17 , but the fifth branch 27 can also extend directly to the tank 2 .

[0076] The thermal treatment circuit 8 also comprises a sixth branch 28 which starts at the output of the second heat exchanger 16, upstream of the separation device 21, and extends as far as the fifth branch 27. The sixth branch 28 allows the reliquefied gas to be returned directly to the tank 2 by bypassing the separation device 21. This bypass serves to prevent unnecessary heat input due to the passage of the gas through the separation device 21. The sixth branch 28 is therefore used when all the gaseous gas circulating in the thermal treatment circuit 8 is reliquefied by passing through the second heat exchanger 16.

[0077] After having circulated through the cooling circuit 17 or after reliquefaction in the heat treatment circuit 8, the liquid gas returns to the tank 2 via at least one end piece 29. The end piece 29 may make it possible to adjust the temperature of the gas contained in the tank 2 and / or the pressure of said tank 2. Thus, the end piece 29 may be an orifice 30 or a sparger member 31. The orifice 30 may be arranged at the bottom of the tank 2.

[0078] By means of the above-mentioned third heat exchanger 19, the temperature of the liquid gas contained in the tank 2 can be reduced. Thus, the liquid gas is extracted from the tank 2, is supercooled by flowing through the third heat exchanger 19, and is returned to the tank 2 in a supercooled state via the orifice 30. Therefore, the overall temperature of the liquid gas contained in the tank 2 can be reduced over time.

[0079] In the case where the end member 29 or at least one of the end members 29 is a spray head member 31, the pressure of the tank 2 can be reduced. The spray head member is used to spray liquid gas in the head space 3 of the tank 2 so as to condense the gaseous gas present in the head space 3, thereby reducing the pressure of the tank 2. In addition, the spray head member 31 can spray liquid gas that has been supercooled by the third heat exchanger 19 in advance so as to enhance the condensation of the gaseous gas in the head space 3 of the tank 2.

[0080] When the generation of gaseous gas in the head space 3 of the tank 2 is not sufficient to satisfy the consumption of the high-pressure gas consumer 4 and / or the low-pressure gas consumer 5, the management system 1 can be configured to supply liquid gas to the consumption of the high-pressure gas consumer 4 and / or the low-pressure gas consumer 5. Thus, the management system can include an additional supply device 33. The latter can, for example, be connected to the cooling circuit 17 so as to benefit from the pump 18 to ensure circulation within the additional supply circuit 33.

[0081] The additional supply circuit 33 is divided into a high pressure channel 34 and a low pressure channel 35, which are respectively used to supply the high pressure gas consumption device 4 and the low pressure gas consumption device 5. The high pressure channel 34 includes a high pressure pump 36 and a high pressure evaporator 37. The high pressure pump 36 pumps the liquid gas to a pressure compatible with the high pressure gas consumption device 4.

[0082] The high-pressure evaporator 37 is used to evaporate the liquid gas subjected to high pressure so that the gas becomes gaseous and can be consumed by the high-pressure gas consumption device 4 .

[0083] The low-pressure passage 35 includes a low-pressure evaporator 38, which evaporates the liquid gas so that the low-pressure gas consuming device 5 can consume the gas if the gas is suitable for supplying the low-pressure gas consuming device 5. The low-pressure passage 35 does not include any pump like the high-pressure passage 34, because the circulation of the liquid gas by the pump 18 is sufficient to pressurize the liquid gas to a pressure compatible with the low-pressure gas consuming device 5.

[0084] The management system 1 may also include a discharge channel 39 connected to the supply channel 6 and extending up to the burner 40. The discharge channel 39 is used to handle the gaseous gas in the head space 3 of the tank 2 to prevent overpressure inside the tank 2 and so that the gaseous gas cannot be consumed or reliquefied.

[0085] In order to determine the paths and the gas pressures within the management system 1, the management system 1 comprises a plurality of expansion elements and a plurality of valves in addition to the above-mentioned expansion member 15 and control member 32. The heat treatment circuit 8 thus comprises a first regulating element 41 upstream of the separation device 21 and a second regulating element 42 arranged on the sixth branch 28. The first regulating element 41 and the second regulating element 42 control the gas flow rates circulating in the branches of the circuit portion under consideration and also control the gas pressure to a lesser extent.

[0086] The valve can be in an open or closed position, depending on the nature of the gas contained in the tank 2 and how it should be used, as will be described in detail below. Thus, the first branch 9 comprises a first valve 43, and if the control member 32 is not capable of regulating the flow of the gaseous gas, the second branch 10 may also comprise a second valve 44 in addition to the control member 32. Furthermore, the third branch 25 comprises a third valve 45, and the fourth branch 26 comprises a fourth valve 46.

[0087] Furthermore, the cooling circuit 17 comprises a fifth valve 47 for allowing the liquid gas to flow through the second heat exchanger 16 .

[0088] Finally, the portion of the supply circuit 6 connecting the first branch 9 to the low-pressure gas consumer 5 comprises a sixth valve 51 .

[0089] Figure 2 and Figure 3 An example of a diagram of the flow of gas within the management system 1 according to the properties of the gas is shown. Figure 2 In the example, the gas contained in tank 2 is methane, and Figure 3 2 is an example of circulation when the gas contained in the tank 2 is ethane. For each graph, a solid line corresponds to a line where the gas circulates or can circulate, and a dotted line corresponds to a line where the gas does not circulate.

[0090] for Figure 2 The gas contained in the tank 2 and that can circulate in the management system 1 is therefore methane, more precisely natural gas mainly composed of methane. Methane can be consumed by the high-pressure gas consumption device 4 and the low-pressure gas consumption device 5 if it is placed at a pressure compatible with the high-pressure gas consumption device 4 and the low-pressure gas consumption device 5.

[0091] Thus, if the natural gas is in the gaseous state in the head space 3 of the tank 2, the latter can be sucked into the supply circuit 6. The gaseous natural gas then flows through the first heat exchanger 13 to capture the calories generated by the gas circulating in the thermal treatment circuit 8, and is then compressed by the compression device 7.

[0092] If the intention is to supply the high-pressure gas consumer 4 , all gaseous natural gas is compressed by the compression device 7 before circulating up to the high-pressure gas consumer 4 to supply the high-pressure gas consumer 4 .

[0093] If the intention is to supply a low-pressure gas consumer 5, the gaseous natural gas is compressed by the compression device 7 until the first compression stage 11, where it is then at a pressure compatible with the low-pressure gas consumer 5, and then partially circulates in the first branch 9 and then circulates again in the supply circuit 6 until the low-pressure gas consumer 5 to supply the low-pressure gas consumer.

[0094] If the intention is to reliquefy the gaseous natural gas, the latter is compressed as far as the second compression stage 12 , circulates in the second branch 10 and is expanded by the control member 32 .

[0095] The gaseous natural gas then flows through the first heat exchanger 13 to be precooled and can be further expanded by the expansion member 15 before flowing through the second heat exchanger 16. In parallel with the above, the liquid gas circulates in the cooling circuit 17 and can also flow through the second heat exchanger 16 in order to at least partially re-liquefy the gaseous natural gas. In order to enhance the re-liquefaction of the gaseous natural gas, the liquid natural gas can be subcooled by flowing through the third heat exchanger 19 before flowing through the second heat exchanger 16. The subcooled natural gas can also be used to reduce the overall temperature of the liquid natural gas by flowing until the orifice 30, or to reduce the pressure in the tank 2 by re-condensing the vapor state due to spraying the subcooled gas through the spray head member 31.

[0096] If the natural gas is completely reliquefied at the output of the second heat exchanger 16 , the latter can flow in a sixth branch 28 in order to return via the cooling circuit 17 to the tank 2 and not through the separation device 21 in order to limit unnecessary heat input.

[0097] If the natural gas is only partially reliquefied, the latter circulates as far as the separation device 21. The liquid portion circulates via the second output 24 in a fifth branch 27 to reach the tank 2 via the cooling circuit 17 and then to the orifice 30. The vapor portion circulates via the first output 23 of the separation device 21 in a fourth branch 26 to reach the supply circuit 6 upstream of the first heat exchanger 13 in order to be consumed or reliquefied.

[0098] Natural gas can be consumed by both gas consumers 4 , 5 , so that liquid gas can also circulate in the additional supply circuit 33 and, in particular, through the high-pressure channel 34 and / or the low-pressure channel 35 if there is insufficient gaseous gas in the head space 3 of the tank 2 .

[0099] for Figure 3 , the gas contained in the tank 2 is ethane. Ethane contains a portion of methane, but the portion is extremely small. The high-pressure gas consumption device 4 can consume ethane, but this is not the case for the low-pressure gas consumption device 5, even at compatible pressures.

[0100] The ethane can be sucked into the supply circuit 6 . The gaseous ethane then flows through a first heat exchanger 13 to capture the calories generated by the gas circulating in the thermal treatment circuit 8 , and is then compressed by the compression device 7 .

[0101] If the intention is to supply the high-pressure gas consumer 4 , all gaseous ethane is compressed by the compression device 7 before flowing to the high-pressure gas consumer 4 to supply the high-pressure gas consumer 4 .

[0102] If the intention is to supply the low-pressure gas consumer 5, the gaseous ethane cannot be supplied directly to the low-pressure gas consumer 5, as described above. For this purpose, the gaseous ethane must first pass through the thermal treatment circuit 8.

[0103] If the intention is to reliquefy the gaseous ethane or indirectly supply the low-pressure gas consumer 5, the gaseous ethane is compressed up to the first compression stage 11 and circulates in the first branch 9 up to the first heat exchanger 13 to be precooled and can be further expanded by the expansion member 15 before flowing through the second heat exchanger 16. In parallel with the above, the liquid ethane circulates in the cooling circuit 17 and can also flow through the second heat exchanger 16 in order to at least partially reliquefy the gaseous ethane. In order to enhance the reliquefaction of the gaseous ethane, the liquid ethane can be subcooled by flowing through the third heat exchanger 19 before flowing through the second heat exchanger 16.

[0104] If the intention is to supply the low-pressure gas consumer 5, the expansion means 15 can be configured to expand the gaseous ethane so that the ethane comes out of the second heat exchanger 16 mainly in the liquid state by flowing through the second heat exchanger 16, but the methane part mentioned above remains in the gaseous state. Since the reliquefaction temperature of methane is lower than the reliquefaction temperature of ethane, the gas comes out of the second heat exchanger 16 at a temperature between the two reliquefaction points of the two types of gas.

[0105] The partly reliquefied ethane then circulates up to the separation device 21 and the gaseous part, i.e. methane, can then supply the low-pressure gas consumer 5 by coming out via the first output 23 and by circulating in the third branch 25 up to the low-pressure gas consumer 5. The ethane can be returned to the tank in the same way as described above.

[0106] If the intention is to completely reliquefy the gaseous ethane, the reliquefied ethane can reach the tank 2 directly via the sixth branch 28 and the fifth branch 27 without passing through the separation device 21.

[0107] If the ethane is only partially reliquefied, it circulates as far as the separation device 21. The liquid part circulates via the second output 24 in a fifth branch 27 to reach the tank 2 via the cooling circuit 17 and then to the orifice 30. If the low-pressure gas consumer 5 is not intended to be supplied, the vapor part circulates via the first output 23 of the separation device 21 in a fourth branch 26 to reach the supply circuit 6 upstream of the first heat exchanger 13 in order to be consumed or reliquefied.

[0108] like Figure 2 As described in , the subcooled ethane circulating in the cooling circuit 17 can also be used to reduce the overall temperature of the liquid ethane by circulating until the orifice 30, or to reduce the pressure in the tank 2 by recondensing the gaseous ethane due to spraying of the subcooled gas through the nozzle member 31.

[0109] With regard to the additional supply device 33 , only the high-pressure passage 34 can be used for supply, since ethane cannot be consumed by the low-pressure gas consumption device 5 .

[0110] Figure 4 represents an alternative embodiment of the management system 1 according to the invention. Only the differences with respect to what has been described above will be discussed and reference will be made to Figures 1 to 3 The description is provided to obtain the structural and functional related features common to the two embodiments.

[0111] Figure 4 The management system 1 shown differs from the management systems described above in that there is no third heat exchanger for cooling the liquid gas circulating in the cooling circuit 17 .

[0112] In contrast, an alternative embodiment of the management system 1 according to the invention comprises an additional branch 48 connected in parallel with the first branch 9 to the first compression stage 11 and extending as far as the tank 2. The additional branch 48 causes the gaseous gas to flow through a heat exchanger 49 configured to carry out a heat exchange between the gaseous gas and the refrigerant fluid circulating in the reliquefaction loop 50. At the output of the heat exchanger 49, the reliquefied gas circulates in the additional branch 48 until it returns to the tank 2.

[0113] Therefore, when it is not possible to overcool the liquid gas in the cooling circuit 17 (which could result in poor reliquefaction of the gaseous gas flowing through the second heat exchanger 16), for example when the temperature difference is too low or when the amount of gaseous gas is too large, the additional branch 48 and the heat exchanger 49 can be used.

[0114] In such a case, it may be sensible to divide the compressed gaseous gas between the heat treatment circuit 8 and the additional branch 48 so that the gaseous gas is effectively reliquefied. Figures 1 to 3 The efficiency is the same as that of the management system described in . Depending on the nature of the gas, reference will be made to the gas paths within the management system. Figure 2 and Figure 3 Description.

[0115] Of course, the invention is not limited to the examples that have just been described and several modifications may be made to these examples without departing from the scope of the invention.

[0116] As just described, the invention does achieve the set objectives and proposes a gas management system that provides for the consumption and / or reliquefaction of gases, whatever their nature. Variants not described herein may be implemented without departing from the scope of the invention, provided that they comprise a management system according to the invention.

Claims

1. A management system (1) for gas contained in at least one tank (2) of a floating structure, the floating structure comprising at least one gas consumption device (4, 5), the management system (1) comprising: at least one gas supply circuit (6) of the gas consuming device (4, 5), the supply circuit (6) comprising at least one compression device (7), the at least one compression device (7) comprising at least two compression stages (11, 12) and configured to compress the gaseous gas extracted from the tank (2) to a pressure compatible with the needs of the gas consuming device (4, 5), at least one circuit (8) for the thermal treatment of the gaseous gas compressed by at least one compression stage (11, 12) of the compression device (7), at least a first heat exchanger (13) configured to carry out heat exchange between the gaseous gas circulating in the supply circuit (6) between the tank (2) and the compression device (7) and the gaseous gas circulating in the heat treatment circuit (8), at least one cooling circuit (17) comprising at least one pump (18) configured to extract liquid gas from the tank (2), at least a second heat exchanger (16) configured to carry out heat exchange between the gaseous gas circulating in the heat treatment circuit (8) and the gas circulating in the cooling circuit (17), downstream of the first heat exchanger (13), Characterized in that the heat treatment circuit (8) comprises at least a first branch (9) connected to a first compression stage (11) of the compression device (7) and a second branch (10) connected to a second compression stage (12) of the compression device (7), wherein the second compression stage (12) is arranged downstream of the first compression stage (11), and the first branch (9) and the second branch (10) are joined together at a convergence point (14) of the heat treatment circuit (8).

2. The management system (1) according to claim 1, wherein: The convergence point (14) is arranged between the compression device (7) and the first heat exchanger (13).

3. The management system (1) according to claim 1 or 2, wherein: The heat treatment circuit (8) comprises at least one expansion member (15) arranged downstream of the first heat exchanger (13).

4. The management system (1) according to claim 3, wherein: The expansion member (15) is arranged between the first heat exchanger (13) and the second heat exchanger (16).

5. Management system (1) according to any one of the preceding claims, wherein: The second branch (10) of the heat treatment circuit (8) comprises control means (32).

6. Management system (1) according to any one of the preceding claims, wherein: The gas consumers (4, 5) are high-pressure gas consumers (4), and the supply circuit (6) is configured to supply the high-pressure gas consumers (4) and / or the low-pressure gas consumers (5).

7. The management system (1) according to claim 6, wherein: The supply of the low-pressure gas consumer (5) by the supply circuit (6) is at least partially carried out via the first branch (9).

8. Management system (1) according to any one of the preceding claims, wherein: The heat treatment circuit (8) comprises a separation device (21), the input (22) of which is arranged downstream of the second heat exchanger (16).

9. The management system (1) according to claim 8, in combination with claim 6, wherein: The separation device (21) comprises a first output (23) configured to allow gaseous gas to exit the separation device (21), and the heat treatment circuit (8) comprises a third branch (25) connecting the first output (23) of the separation device (21) to the supply circuit (6) of the low-pressure gas consumer (5).

10. The management system (1) according to claim 9, wherein: The heat treatment circuit (8) comprises a fourth branch (26) connecting the first output (23) of the separation device (21) to the supply circuit (6) at a point located between the tank (2) and the first heat exchanger (13).

11. The management system (1) according to claim 10, wherein: The separation device (21) comprises a second output (24) configured to allow liquid gas to exit the separation device (21), and the heat treatment circuit (8) comprises a fifth branch (27) connecting the second output (24) of the separation device (21) to the cooling circuit (17).

12. The management system (1) according to claim 11, wherein: The heat treatment circuit (8) includes a sixth branch (28) which connects an output portion of a passage of the second heat exchanger (16) constituting the heat treatment circuit (8) to the fifth branch (27).

13. The management system (1) according to any one of the preceding claims, comprises a third heat exchanger (19), which is configured to implement heat exchange between the liquid gas circulating in the cooling circuit (17) and the refrigerant fluid circulating in the cooling loop (20).

14. The management system (1) according to any one of claims 1 to 12, comprising an additional branch (48) connecting the first compression stage (11) of the compression device (7) to the tank (2), the management system (1) also comprising a heat exchanger (49), the heat exchanger (49) being configured to implement heat exchange between the gaseous gas circulating in the additional branch (48) and the refrigerant fluid circulating through the reliquefaction loop (50).

15. Management system (1) according to any one of the preceding claims, wherein: The cooling circuit (17) comprises at least one end part (29) opening in the tank (2), the end part (29) being a spray head member (31) and / or an orifice (30) arranged in a lower part of the tank (2).

16. A floating structure comprising at least one tank containing liquefied natural gas and a management system (1) according to any one of the preceding claims.

17. A floating structure comprising at least one tank (2) containing ethane and a management system (1) according to any one of claims 1 to 15.

18. A method of managing gas contained in at least one tank (2) of a floating structure, said method being implemented by a management system (1) according to any one of claims 1 to 15, during which: If the gas contained in the tank (2) is liquefied natural gas, the gas circulates through the first branch (9) and / or the second branch (10) of the thermal treatment circuit (8), or, If the gas contained in the tank (2) is ethane, the gas circulates in the first branch (9) of the thermal treatment circuit (8) and the circulation of the gas in the second branch (10) is blocked.

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